1. Field of the Invention
This invention relates to novel rubber compositions, and more particularly to a rubber composition having improved wet skid resistance and rolling resistance suitable for use in tire tread.
2. Description of the Prior Art
Lately, it has seriously been taken as rubber performances for automobile tire tread to improve the wet skid resistance, heat build-up and durability in relation to running stability as well as the rolling resistance or hysteresis loss in relation to the fuel consumption.
Heretofore, it was difficult to satisfy the above performances with a single rubber, so that blends of different rubbers have been proposed. For example, rubber compositions each containing a blend of styrene-butadiene copolymer rubber and polybutadiene rubber have widely been used as a tread rubber for automobile tire. In these rubber compositions, however, the rolling resistance (hysteresis loss) was not necessarily low and also the wet skid resistance was not sufficient, because there were required such conflict conditions that a substance having a low glass transition temperature was used as a means for improving the rolling resistance, while a resin or the like having a high glass transition temperature was used as a means for improving the wet skid resistance. Furthermore, they had a problem that compatibility and dynamic properties, particularly heat build-up lowered considerably.
Therefore, it was difficult to improve the wet skid resistance without damaging the rolling resistance.